Ceramic compositions and articles made therefrom

Abstract

This invention relates to slurry compositions which are adapted for the formation of ceramic articles. The compositions comprise ceramic particulate matter blended with an aqueous dispersion of an internally plasticized thermosetting resin. These compositions are formed into green (unfired) ceramic tapes which can be ultimately used for electronic purposes wherever fired rigid ceramic bodies are required. The use of these compositions overcomes many of the prior disadvantages relating to dimensional stability, flexibility, atmospheric stability and compatibility with a wide variety of conventional metallizing pastes.

I claim: 
     
       1. In a process for preparing green flexible films by casting films on a supporting surface with dispersions of ceramic particulate matter, resins and liquid and drying to form a green sheet, the improvement of casting such films with a slurry composition adapted for the formation of flexible green ceramic articles which have an initial modulus below 20,000 psi and which have excellent dimensional stability and solvent resistance, said composition comprising ceramic particulate matter blended with an aqueous dispersion of an internally plasticized thermosetting resin, said resin containing from 0.1 to 10 weight percent of a comonomer which after polymerization is capable of cross-linking the polymer by heat treatment and (a) from 50 to 95 weight percent vinyl acetate, and from 4.9 to 49.9 weight percent of an internally plasticizing comonomer; (b) from 50 to 98 weight percent of an ester of a 1 to 8 carbon atom alcohol and acrylic acid and the remainder a plasticizing comonomer; or (c) from 50 to 84.9 weight percent ethylene and from 15 to 49.9 weight percent of a plasticizing comonomer, there being from 85 to 97 parts of said ceramic particulate matter and from 3 to 15 parts of said resin, the ceramic particulate matter having a particle size no larger than 44 microns then heating the film at from about 50 to about 150° C. to remove the aqueous medium and to  cause the resin to cross-link whereby a flexible film loaded with ceramic particulate matter, having excellent dimensional stability and solvent resistance is provided. 
     
     
       2. The process of claim 1, wherein the resin is resin (a). 
     
     
       3. The process of claim 2 wherein the plasticizing comonomer is selected from the class consisting of ethylene, esters of 1 to 8 carbon atom alcohols and any of maleic acid, fumaric acid, or acrylic acid and esters of 4 to 8 carbon atom alcohols and methacrylic acid. 
     
     
       4. The process of claim 1 wherein the resin is resin (b). 
     
     
       5. The process of claim 4 wherein the plasticizing monomer is selected from the class consisting of ethylene, esters of 1 to 8 carbon atoms alcohols and either maleic acid or fumaric acid and esters of methacrylic acid and an alcohol having up to 8 carbon atoms but having at least 2 more carbon atoms than the alcohol portion of the acrylic acid ester. 
     
     
       6. The process of claim 5 wherein the acrylic ester comonomer comprises from 50 to 75 weight percent of the copolymer.